energy recovery ventilator

An energy recovery ventilator is a device similar to a heat
recovery ventilator (HRV) but that also includes a humidity regulator
to remove excess humidity (or add humidity) to the air that is being brought
into a house. Energy recovery ventilators (ERVs) are especially suited for
use in climates where cooling loads place strong demands on HVAC systems.
However, ERVs are not the same as dehumidifiers.
What they do is transfer moisture from the humid air stream – the
incoming outdoor air in summertime – to the exhaust air stream. The
desiccant wheels used in many ERVs become saturated quite quickly and the
moisture transfer mechanism becomes less effective with successive hot,
humid periods. In some cases, ERVs may also be effective in climates with
very cold winters. If indoor relative humidity tends to be too low, what
available moisture there is in the indoor exhaust air stream is transferred
to incoming outdoor air.